1. Field of the Invention
The present invention relates to a carriage traveling mechanism for a floppy disc drive, and more particularly to an improvement of the traveling mechanism which reciprocally drives the carriage by use of an .alpha. belt.
2. Prior Art
As one of the various external data recording media for computers there has been known a so-called floppy disc which includes a planer flexible plastic sheet having one or both sides coated with electro-magnetic recording layers and which is increasingly used over a wide range of applications because of its various advantages such as low price, ease of handling, the possibility of random access, etc. as compared with conventional hard discs.
In order to write and read the data to and from the floppy disc, a floppy disc drive is used in which the floppy disc is rotated at a high speed and a head is closely positioned on the requested track. Therefore, it is necessary that a carriage carrying the head be driven and transferred with high accuracy in order to quickly and firmly move the head to the requested track.
In the prior art devices the carriage is moved by a screw or belt. In recent years, however, there has been utilized a carriage traveling mechanism in which a part of a belt is wound around a drive shaft with both ends of the belt fixed to the carriage and the rotation of the drive shaft is converted into the reciprocation of the carriage. This device has been know as an .alpha. belt drive since the belt is mounted around the drive shaft in an .alpha. shape.
According to the .alpha. shape drive mentioned above, a guide pulley which is separately prepared other than the drive shaft of the belt traveling mechanism in the prior art device can be omitted. Therefore, the drive shaft and the carriage can be closely arranged and the mechanism has the advantage of being designed to be small in size.
In the conventional .alpha. belt feeding mechanism, however, the belt is loosened by stretching caused by temperature fluctuations which remarkably decrease the accuracy of carriage feeding and affect the accuracy of read and write action.
Furthermore, in the prior art devices, oscillation is easily generated in the belt itself during carriage movement and the read and write operations must be delayed until the oscillation mentioned above decreases after the head is positioned on the track to which the head is required to be positioned. Therefore, in the prior art devices, the belt is assembled in a state with a desired pre-tension or the belt is fixed to the carriage with an end of the belt connected to a spring. In the former case several troublesome operations are required in its assembly and the belt is easily broken; and in the latter case it is hard to obtain stable tension. Moreover, in the prior art devices, both ends of the belt mentioned above are fastened to belt receiving portions provided on the carriage by spot welding, screwing, riveting or the like. Screwing and the riveting are troublesome fastening operations and spot welding does not provide accurate positioning in the reciprocal slides of the carriage.